Method of manufacturing semiconductor device with a multi-layered gate dielectric

Abstract

A method of manufacturing a semiconductor device includes forming a first nitride semiconductor layer, forming thereover a second nitride semiconductor layer having a band gap wider than that of the first nitride semiconductor layer, and thereby forming a stacked body, etching the stacked body with a first film placed over the stacked body and including a first opening portion as a mask to form a trench penetrating through the second nitride semiconductor layer and reaching an inside of the first nitride semiconductor layer, causing an end portion of the first film to retreat from an end portion of the trench, forming a second film over the first film including the inside of the trench, and forming a gate electrode over the second film.

What is claimed is: 
     
       1. A method of manufacturing a semiconductor device, the method comprising:
 forming a first nitride semiconductor layer, forming thereover a second nitride semiconductor layer having a band gap wider than that of the first nitride semiconductor layer, and thereby forming a stacked body; 
 forming a first film, including a first opening portion, over the stacked body; 
 forming a mask film over the first film, wherein the mask film is retreated from a first end of the first opening portion; 
 etching the stacked body using a stacked film, comprising the first film and the mask film, as a mask to form a trench penetrating through the second nitride semiconductor layer and reaching an inside of the first nitride semiconductor layer; 
 causing an end portion of the first film to retreat from an end portion of the trench by etching the first film with the mask film as a mask, and removing the mask film; 
 after causing the end portion of the first film to retreat, forming a second film covering the first film and an inside of the trench; and 
 forming a gate electrode over the second film. 
 
     
     
       2. The method of manufacturing a semiconductor device according to  claim 1 , wherein causing the end portion of the first film to retreat includes causing the end portion of the first film to retreat by 0.2 μm or greater from the end portion of the trench. 
     
     
       3. The method of manufacturing a semiconductor device according to  claim 1 , wherein the first film includes a film containing silicon nitride, and
 wherein the second film includes a film containing aluminum oxide.